Edge 25 offers all the necessary stats to take your ride to the next level. Small in size, yet packed with features such as smart notifications when paired with a smartphone.

Choose from courses ridden by others or create your own on Garmin Connect, Garmin's free online community. Once you choose a course, upload it directly to Edge 25 and follow it to your destination. You can even compete against yourself to make it more interesting. Via Bluetooth with your smartphone or a simple connection to a computer, you can upload your activities to Garmin Connect and see the path you traveled on a map, analyze it, share it and view details. Bluetooth also allows Live Tracking, so friends and family can follow your ride in real time. Invite followers using email or social media, which lets them view your live data on Garmin Connect. Compete against other cyclists on Garmin Connect segments and see your results post-ride on the leaderboard. Includes on-device alerts for segment start/finish points.

Edge 25 uses GPS/GLONASS satellites to track how far/fast and where you ride, even under dense tree cover. Unlike a phone, you can use Edge 25 for up to 8 hours without worrying about data or battery drainage.

Finally had to replace my Edge 305, which I had for somewhere around 10 years I guess.
I wanted a GPS with HR and Cadence and an easy-to-read screen, something not too big for the mountain bike, fairly accurate with tracking. The Edge 25 does all that. I didn't have to change my sensors, either. It works great on my MTB and tracks fairly well, except under dense tree cover. Even with GPS and GLONASS, heavy vegetation can block it.
It's a bit fiddly to get a course loaded to the 25, but when you do, it works well. I set display scroll on slow and the navigation becomes another screen that will pop up when approaching a turn.
But battery life for long rides? Abysmal. I get 6-6.5 hours max battery life ... a touch more if I turn off GLONASS. A device this small should last triple that.
If I was buying just for my mountain bike or short road rides, this is a great little unit. Anybody touring or riding centuries needs to look for one of the bigger units or carry a battery charger and the proprietary USB cable.

Easy to program and operate, kinda. Sometimes it takes quite awhile to locate GPS and will not operate until this process is complete. I have looked in the sky during these times to see if our satellites were crashing to earth after a missile assault. In addition only 8 hours of battery life is marginal at best. As it is GPS it is more accurate than a standard bike computer.

This little computer does everything I want it to do. Out of the box it comes with firmware vs 3.0 which I immediately upgraded to the current 3.3 via Garmin Connect. Pairing the speed sensor was pretty much a straight forward process although the instructions as to how to do that were a little sketchy. After it is paired you must actually ride the bike approximately one mile with the GPS working to calibrate the sensor to your wheel size. In times past, you actually had to put the edge into the "indoor" mode to cause the speed sensor to work; that is no longer the case. The sensor will automatically take over when gps signal is dropped. Likewise, when you put your bike on an indoor trainer the speed sensor will take over when there is no GPS signal.
The computer allows you to show three data fields on page one; it allows two data fields on the second. It is very easy to set up - I had mine all dialed in without even opening the instruction manual. Reading the manual after words allowed me to pick up a few subtle nuances.
You can download/upload tracks from Garmin Connect but the map is a a rudimentary presentation. It does allow you to use turn by turn to aid in navigation. If you want more, you'll have to spend more to get one of the mapping GPS.
I'm not a smart phone user and thus didn't attempt to pair this to a smart phone with the bluetooth feature and can't say how that process or application works.
I would highly recommend this for someone looking for a small, easy to use GPS driven bicycle computer who doesn't need all the bells and whistles. One caveat, upgrade to firmware 3.3 before using.